Liquefied gas refrigeration system



M r h 2, 1966 c. F. FRlTCH, JR, ETAL 3,241,329

LIQUEFIED GAS REFRIGERATION SYSTEM INVENTORS CARL E FRITCH, JR.

2 Sheets-Sheet 1 HENRY M. TIEDEMANN ATTORNEY Filed Sept. 6, 1963 M r h 22, 1966 c. F. FRITCH, JR, ETAL 3,241,329

LIQUEFIED GAS REFRIGERATION SYSTEM 2 Sheets-Sheet 2 Filed Sept. 6, 1963 INVENTORS CARL E FRITGH, JR. HENRY M.T|EDEMANN ATTORNEY United States Patent O 3,241,329 LIQUEFIED GAS REFRIGERATION SYSTEM Carl F. Fritch, .lr., Glen Ellyn, Ill., and Henry M. Tiedemann, Greenwich, Conn., assignors to Chemetron Corporation, Chicago, 11]., a corporation of Delaware Filed Sept. 6, 1963, Ser. No. 307,152 8 Claims. (CI. 6252) The present invention relates to a refrigeration system employing as refrigerant a liquefied gas having a low boiling point such as liquefied nitrogen, and more particularly to an improved method and apparatus for preserving frozen and perishable goods such as food products during storage and transportation from place to place: for example, by various transport means such as motor trucks, ships, airplanes, and railroad cars.

Liquefied gas refrigeration systems have been proposed :before. However, known liquefied gas refrigeration systems have not attained wide acceptance because of certain limitations. One of these systems employs liquid nitrogen distributed by a spray header disposed along the ceiling of a cold storage compartment in a truck for transporting food products. The liquid nitrogen header is provided with a series of spaced openings and is in communication with a supply of liquid nitrogen via a conduit having a temperature controlled valve disposed therein. When a predetermined temperature is sensed by the valve control, the valve opens, releasing nitrogen in the form of vapor, or mixed vapor and liquid, which falls from the header upon the food or other refrigerated products stored in the compartment thereby cooling them and the atmosphere of the compartment. Although this known system quickly cools the compartment, the very cold liquid nitrogen particles (approximately -320 F.) in the spray will cause damage to certain perishable food products such as lettuce due to freezing action. Moreover, this prior art system is inherently somewhat dangerous as the truck operator may he in the storage compartment at the precise time the very cold liquid nitrogen is being sprayed from the header. As nitrogen at this very low temperature in contact with the skin can cause severe injury and as nitrogen vapor will not support life it is apparent that there are certain disadvantages in the use of such a system. Although additional controls may be provided to prevent opening of the valve when the compartment is occupied by a person, substantial additional cost is entailed and nonetheless, there is still the possibility that a component will fail under conditions resulting in bodily injury. Moreover, if an additional door control is added for safety reasons, opening of the compartment door will temporarily disable the refrigeration system even if more cooling is required to preserve the quality of the food at that time.

Systems for controlling the moisture content in the insulation of cold storage rooms by passing cooled air between inner and outer spaced wall surfaces of the cold storage room are known. Examples of such systems are disclosed in United States Letters Patent 2,485,630; and 2,623,364, granted to C. G. Munters. The present invention discloses a method and apparatus combining certain features of the aforementioned systems with newly discovered modifications to provide an improved liquefied gas refrigeration system in which cooling is achieved by passing cold vapor between inner and outer spaced wall surfaces of a refrigerated compartment thereby eliminating the necessity for spraying or direct injection of cold liquid refrigerant into the compartment and the resulting danger of bodily injury or damage to food products.

It is therefore an important object of the invention to provide an improved apparatus and method for refrigerating a storage compartment by passing cold vapor ice through passages in its heat insulated walls to cool the compartment.

A further object is to provide improved liquefied gas refrigeration apparatus including means for rapidly chilling a storage compartment.

Another object is to provide improved refrigeration apparatus including means for providing an inert atmosphere for a refrigerated compartment.

A further object is to provide an improved liquefied gas refrigeration system including means for eliminating the accumulation of moisture in the insulation by passing dry vapor through passages in the heat insulated Walls of the system.

Still another object of the invention is to provide an improved method for refrigerating a compartment including steps of vaporizing cold liquefied gas, and passing cold vapor through heat exchange apparatus in efficient heat transfer relationship with the refrigerated compartment.

A still further object is to provide an improved liquid nitrogen refrigeration system which takes full advantage of both the latent heat and the sensible heat of the nitrogen during cooling for optimum efficiency.

Still another object is to provide an improved liquid nitrogen refrigeration system adapted for use in refrigerated containers transportable by motor truck, rail car, airplane or ship.

A further object is to provide an improved refrigerated container adapted for use in a cold liquefied gas refrigeration system.

Another object is to provide an improved refrigerated container system adapted for use on seagoing vessels.

Still another object is to provide an improved refrigeration system for use on local delivery trucks.

Briefly stated, and exemplified in an illustrated embodiment of the present invention, there is provided a liquid nitrogen refrigeration system comprising a refrigerated compartment having heat insulated wall portions including a network of vapor channels formed therein for passage of cold vapor. One or more wall, ceiling or floor surfaces of the refrigerated compartment is in heat transfer relationship with certain of the channels. Associated in efiicient heat transfer relation with the compartment is a vaporizer for vaporizing cold liquefied gas, which is in communication with the network of vapor channels and which is adapted for communication with a vessel of cold liquefied gas.

In the system there is an adjustable temperature control means which may be set at a predetermined desired temperature level. The control means is operated by vapor pressure generated in the refrigeration system eliminating the need for an external power source to operate the control means. The control means is so arranged that when the temperature within the compartment rises above the predetermined and pre-set level, a sensing means, forming part of the control means, senses this temperature rise and through the operation of the control means causes a valve to open. On opening of the valve, cold liquid and/ or cold vapor from the vessel of liquefied gas, due to pressure in the vapor space of the vessel, will enter the vaporizer and cold vapor will be released from the vaporizer outlet and pass into the connected end of the network of vapor channels or passages to cool the compartment. The cold vapor will continue to flow through the passages and ultimately out the end of the network connected to atmosphere due to pressure differentials along the passages, until sufficient heat has been extracted from the compartment and its contents to cause the temperature to again drop to the predetermined level. When this predetermined temperature level is sensed by the sensing means, the control means actuates closing of the valve and temporarily interrupts flow of cold vapor.

Cold liquid flow to the vaporizer will also cease due to the increase in pressure in the vaporizer on closing of the valve. As the temperature again rises, this temperature increase is sensed causing the system cycle to repeat, and thus the temperature is continuously maintained at the desired level. It will 'be apparent that the flow of cold vapor in the passages in the walls around the shipping container compartment forms a heat sink shield for thorough protection of the refrigerated contents of the compartment although the network of passages is normally isolated from fluid communication with the compartment.

The invention, both as to its organization and method of operation, together with further objects and advantages, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 illustrates a diagrammatic View of an embodiment of the invention, partially in perspective, and partially in section and broken away to illustrate details;

FIG. 2 is a fragmentary sectional view in perspective of a portion of the wall of the refrigerated container shown in FIG. 1;

FIG. 3 is a fragmentary sectional plan view of the refrigerated container shown in FIG. 1, partially broken away to show details;

FIG. 4 is a fragmentary sectional view of a portion of the vaporizer of FIG. 1; taken along the line 44 of FIG. 1;

FIG. 5 is a fragmentary sectional view of a portion of the vaporizer of FIG. 1 taken along the line 5-5 of FIG. 1;

FIG. 6 is a fragmentary plan view, partly in section, of a multiple refrigerated container system suitable for a seagoing ship; and

FIG. 7 is a perspective view, partially broken away, showing an embodiment of the invention adapted for use on a motor truck.

Referring now to the drawings, and particularly to FIGS. 1, 2 and 3, the present invention is illustrated embodied in a refrigerated container 10 which in one form may be adapted for transport by motor truck, rail car, plane, or on a seagoing ship. The refrigerated container 10 may take the form of a rectangular box-like structure as shown in FIG. 1 having an external sheathing 11 which may be of sheet metal such as aluminum, enclosing and spaced from internal wall means 12 having etficient heat transfer characteristics, which may advantageously be of sheet metal such as aluminum or steel, forming a refrigerated compartment 13. The compartment 13 is adapted for storage and transport of food or other products requiring refrigeration, and is provided with a suitable door 9 (FIG. 3) at one end for access purposes. The external sheath 11 and the internal wall structure 12 are spaced apart by suitable heat insulation 14 which may advantageously be an insulating material such as polystyrene or polyurethane or a combination of insulations. As shown in FIG. 2 the insulation 14 includes a layer of polystyrene 15, and a layer of polyurethane 16. A suitable vapor barrier 18 of asphalt backed up by aluminum foil or equivalent may advantageously be pro vided between the sheathing 11 and the insulation 14..

The refrigerated container 10 includes apparatus for eflecting refrigeration of the compartment 13 comprising an insulated low boiling point liquefied gas supply container 20 which includes an inner vessel 21 which is suspended or otherwise supported within an external casing 22 providing an insulating space completely surrounding the inner vessel which space may be under vacuum and filled with insulating material of a character that is very effective for reducing the flow of heat to the cold body of liquefied gas 24 disposed within the inner vessel. The body of liquefied gas 24- may advantageously be in the form of liquid nitrogen which has a temperature of approximately 320 F. The inner vessel 21 may also be provided with the customary liquid level test con nections, and relief valves which are not shown in the interest of clearness of the drawings.

The refrigeration apparatus includes means forming a heat exchanger 30 (FIG. 1) for cooling the refrigerated compartment 13 comprising a vaporizer 25 in communi cation with the body of cold liquid in vessel 21 via a suitably insulated line 26, and a network 31 (FIGS. 1-4) of long connected spaces formed in the insulation in the walls, ceiling and floor of compartment 13, in heat transfer relation with them, connected in series with vaporizer 25 via a line 27. The vaporizer 25 may advantageously be mounted in the ceiling of compartment 13 (FIGS. 1 and 4) and therefore has a wall portion in efficient heat transfer relationship with compartment 13. Line 26, connecting vessel 21 to vaporizer 25, may advantageously be provided with a liquid shut-off valve 29. The vaporizer 25 may be fabricated from aluminum or other suitable material and is connected to receive fluids, consisting of liquid nitrogen and nitrogen vapor, directly from the vessel 21 via line 26. The vaporizer 25 may advantageously be constructed with liquid line 26 entering its upstream end and with line 26 having a portion or inner conduit 26a thereof extending substantially to the further end of the vaporizer 25 so that cold vapor evolved from the liquid in the vessel 21 and vaporizer 25 can only exit from the vaporizer 25 and enter spaces 31 by Way of an outlet line 27 connected at the same end of the vaporizer 25 as the inlet of the liquid line 26. Therefore, liquid must travel the length of the line 26 and out through portion or inner conduit 26a before it can enter the outer conduit of the vaporizer 25. For this reason liquid entering vaporizer 25 is substantially vaporized before it leaves the vaporizer 25.

The system of the present invention includes means to ensure that under heavy demand conditions excess amounts of liquid nitrogen are not released into the network of channels 31, comprising a ball type float valve 25a shown in FIG. 5 which is mounted within vaporizer 25 in a suitable cage 25b directly below the entrance to vapor outlet line 27. Relatively large quantities of liquid received within vaporizer 25 will cause ball valve 25a to float upward until it seals off outlet 27. Therefore, no liquid can enter the vapor outlet line 27 or the network of vapor spaces 31 downstream thereof. Closing of outlet 27 by ball valve 25a will cause pressure to build up in vaporizer 25 and force liquid back to the vessel 21, eventually causing valve 25a to drop back into cage 25b, permitting cold vapor to escape from vaporizer 25 via now open line 27. This feature positively prevents undue use of liquid gas under excess demand conditions and prevents carry over of liquid nitrogen into the channels.

The system of FIG. 1 includes means for controlling the passage of cold vapor through the heat exchanger comprising a pneumatic or fluid pressure operated controller 40 including temperature sensing means comprising a sensing bulb 41 disposed in the compartment 13 to sense temperature conditions therein, connected to controller 40 by a capillary tube 42. A line 43 connects the controller 40 to a temperature controlled valve 44 in the outlet line 27 of the vaporizer 25. The controller MP is operated by vapor pressure generated by the refrigeration system of the present invention, and to accomplish this is in communication with the vapor space 55 in vessel 21 by way of lines 56 and 57, a shut-off valve 58a, and lines 58, 54, and 60. A regulator 61 may be disposed in line 56 (FIG. 1) to provide a uniform pressure to operate the controller 40. As the system control means comprising controller 40 is thus operated by vapor pressure generated by the refrigeration system of the present invention, no external power source is required to operate the control means.

A vapor outlet line 27a (FIGS. 1 and 4) extends cen trally of container 10 downstream from valve 44 to a T-connection having outlet branch lines 27b, and 270, connecting in turn, to headers 27d and 27e extending parallel to the longer side of container 10. The headers 27d and 27e have a series of spaced vapor openings 27 therein, in registration with horizontal grooves in the insulation in the ceiling of compartment 13 forming ceiling channels 31a forming part of the network of connected spaces 31. As shown in FIG. 1, the network 31 of connected spaces includes parallel ceiling channels 31a, mentioned above, communicating with vapor openings 27 and extending transverse to the longer side of container 10, vertically extending side wall insulation channels 31b which carry vapor from the ceiling channels 31a down below the floor level, horizontally extending floor insulation channels 310 extending from the respective channels 31b transversely to a central header 31d extending substantially from one end of the container to a transverse floor header 31:: (FIG. 3) at the other end, and vertically extending channels 31 in the insulation of the end Wall comprising the door 9 (FIG. 3) which communicate with vent fittings 88 for venting the exhausted vapor to atmosphere. As shown and described, the individual channels 31a, 31b, 31c, 31d, 31c, and 31 are generally parallel to adjacent channels and adjacent portions of the walls, ceiling, and floor of compartment 13.

When valve 44 is open, cold vapor passes from vaporizer via centrally disposed line 27a, 27b, and 170 and transversely via channels 31a across the ceiling, down channels 31b to the floor portion of container 10, across channels 310 to the header 31d, along header 31d to header 31a, and up the end wall channels 317 and out to atmosphere via vent fittings 88. The described flow of cold vapor, therefore, provides means for intercepting heat leakage from the exterior of the container 10 before it can enter the compartment 13, and provides a cold envelope substantially enclosing the refrigerated compartment 13. The described passage of cold vapor through the vapor spaces 31 efficiently cools compartment 13 without resort to a forced circulation of refrigerant over the contents of compartment 13. There will, of course, be some circulation of the atmosphere within compartment 13 due to convection currents, but this circulation will be of a low velocity non-forced type with substantially no drying of the contents of the refrigerated compartment.

Although the spaces 31 are shown as channels in FIGS. 1 and 2, it will be appreciated that if desired, the cooling effect can be increased by elimination of the ridge of insulation indicated at 19 ('FIG. 2) between adjacent chan nels 31 to provide substantially open spaces around the compartment 13.

In order to facilitate an efiicient and positive transfer of fluid from the vessel 21 containing the supply of liquid nitrogen 24 to the heat exchanger 30, means for increasing the pressure on the liquid nitrogen in the ves' sel 20 are provided comprising a pressure building coil 50 (FIG. 1) in communication with the lowest portion of the liquid nitrogen inner vessel 21 via a fill line 51 and a shut-off valve '87, and extending outside the insulated shell of container 20 via a coil portion 52 which is exposed directly or indirectly to the heat of the atmosphere. The insulation around the lines leading from valves 84 and 87 to vessel 21 is indicated in broken line in FIG. 1. Opening of valve 87 will permit liquid to enter coil portion 52 where it will absorb heat from the atmosphere causing the liquid to vaporize, increasing the pressure on the liquid 24 in vessel 21. The coil 50 is connected to the vapor space 55 in the top of the vessel 21 by coil portion 52, and conduit 53.

The system shown in FIG. 1, although arranged to maintain compartment 13 isolated from the cold vapor in channels 31 during regular operation of the system to ensure against bodily injury and adverse effects to perishable food products stored in compartment 13, also includes means for rapidly cooling compartment 13 com prising a spray header 70, which may advantageously be centrally disposed in an upper portion of the compartment 13, along its ceiling, which is in communication with the vessel 21 via a line 74 connecting to line 26. The spray header may advantageously consist of a length of pipe 73 closed at the downstream end, and including a series of spaced openings 72 located over the load space in the compartment 13. The line 74 including the spray header is provided with a manually operable shut-off valve 75 dis posed outside compartment 13 for controlling the transfer of liquid from the vessel to the spray header. The spray header is advantageous in that at times it may be desirable to quickly cool compartment 13 to a desired temperature, as for example, when a warm load is placed in compartment 13 to be refrigerated. All that is necessary for quick cool-down of the load and compartment 13 is to open the valve 75 which releases a spray of very cold nitrogen liquid and vapor directly over the load causing the load and the compartment to quickly cool to a desired temperature level. The manual operation and outside location of valve 75 ensures that cold nitrogen will not be released when the operator is inside compartment 13. The cold vapor released into compartment 13 during cool-down is passed through the network of cooling passages 31 before being vented to atmosphere via a line 70a connecting compartment 13 with line 27a (FIG. 1) provided with a check valve 70b. This provides further cooling of compartment 13 and efi'iicent use of the cooling properties of the cold vapor.

The system shown in FIG. 1 also includes means for providing an inert atmosphere within the refrigerated compartment 13. An inert atmosphere is considered advantageous in preserving certain food stuffs such as lettuce. The means for providing this inert atmosphere comprise an open ended conduit 50 extending into compartment 13 which is in communication with the vapor line 27a, and which is provided with a manually operable valve 81 disposed outside compartment 13. Opening of the valve 81 will release inert nitrogen gas from the open end of the conduit 50 which will enter the compartment 13 and thus provide the desired inert gas atmosphere.

Before operation of the present invention, the vessel 21 may be substantially filled with liquid nitrogen 24 from a convenient source such as a liquid nitrogen transport vehicle (not shown) by way of a fill line 83 projecting from container 20 provided with a fill and drain valve 84.

It is a feature of the system shown in FIG. 1 that cold vapor evolved from the liquefied gas entering vessel 21 during filling operations may be passed through the network of cooling passages 31(including channels 31a, 31b, etc.) to pre-cool compartment 13 before being vented to atmosphere via openings 88 instead of being vented directly to atmosphere. This is accomplished by the provision of a line 89 connected to vapor outlet line 27a, a vent valve 85 in line 89, and a line 86 connected between valve 85 and line 60. This structure provides means for utilizing the cooling power of the nitrogen. vapors flashed 011 during filling operations which would otherwise be Wasted. As the system of FIG. 1 is a closed system, i.e., compartment 13 is normally isolated from the cooling passage network 31, cooling of container 10 and compartment 13 can be carried out with cold vapor evolved from the filling operation during the loading of compartment 13.

During filling operations vent valve 85, in line 86 connected by a T-connection to line 54 communicating with vapor space 55 (as shown in FIG. 1), is open, as is fill and drain valve 84. After the vessel 20 is provided with a supply of liquid nitrogen via line 83 and compartment 13 is pre-cooled by the vapors flashed during the filling operation as described above, the system is ready for operation. The valves 84 and 85 are then closed, and a liquid shutoff valve 29 in line 26 is closed also. Heat leak into vessel 21 will then cause liquid 24 to vaporize and the vapor pressure in space 55 to increase. This operation can be accelerated by opening pressure building shut-off valve 87 controlling flow of liquid to pressure building coil 50 as described above. After the system is pressurized as just described, the controller 40 may be set by means of an adjustment knob 19 (FIG. 1) to a desired temperature level and the liquid shut-off valve 29 is then opened. If the compartment 13 has not previously been cooled down the temperature controller 40 will operate to cause the temperature responsive valve 44 to open whereupon cold liquid nitrogen will pass through the line 26 to the vaporizer 25, and a flow of cold vapor evolved from the liquid in vessel 21 and vaporizer 25 through the heat exchanger will be initiated. As vaporizer 25 is in efficient heat transfer relationship with compartment 13, vaporization of the liquid in vaporizer 25 will be at a rate which is proportional to the temperature in compartment 13. Heat from compartment 13 and the load therein will thus cause liquid in vaporizer 25 to vaporize and the cold vapor to pass via now open valve 44 and vapor line 27 into the network of passageways 31 in the walls of the container 10, cooling compartment 13 and its contents, and then to pass out to atmosphere through exhaust openings 88. It will be recognized that the flow of cold vapor through the network of passages 31 as described above occurs because of the higher pressures in the passages upstream of the exhaust openings 88. Cold vapors will continue to pass from vaporizer 25 through the network of passageways 31 on the exterior of the Walls 12 enclosing the refrigerated compartment 13 until the predetermined temperature set by controller adjustment knob 19 is sensed by the sensing bulb 41. Operation of the controller then closes the valve 44, temporarily shutting of passage of nitrogen vapors through the heat exchanger 30 which includes vaporizer 25 and the cooling passage network 31. With valve 44 closed, pressure build-up in vaporizer 25 prevents liquid transfer from vessel 21 to vaporizer 25. As heat is absorbed in the refrigerated compartment 13, the resulting increase in temperature will be sensed by the sensing bulb 41 and it will again actuate opening of the valve 44 initiating a flow of cold vapor through the heat exchanger 30 including spaces 31 to cool compartment 13. The system will cycle continuously in the fashion outlined providing a uniform desired cold temperature in compartment 13. As the liquid is vaporized in vaporizer 25 which is in efficient heat transfer relationship with the compartment 13 and as the resulting cold vapors are passed about the walls of compartment 13 to cool it and its contents it is apparent that the system of the present invention is of optimum efficiency as it takes substantially full advantage of both the latent heat and the sensible heat of the nitrogen during the cooling cycle.

The heat insulation of the system is maintained at substantially maximum efficiency because the flow of cold dry vapor through the insulation spaces keeps the insulation dry, and the pressure of the dry vapor prevents any significant moisture infiltration into the insulation spaces.

It will be recognized by those skilled in this art that the invention described above provides an improved refrigeration method in which a body of liquefied gas is maintained within a closed container 20 at a temperature of approximately 320 F, Well below the temperature of the refrigerated compartment. The vapor evolved from the body of liquefied gas in vessel 20, line 26 and vaporizer 25 is collected and the vapor is released from time to time by opening valve 44 when a predetermined temperature level is sensed in the interior of the refrigerated compartment 13. The released cold vapor is passed over the exterior wall surfaces 12 of the refrigeration compartment 13 thereby cooling it. The above operations are conducted while maintaining the compartment 13 isolated from the cold nitrogen. Therefore, the contents of the compartment 13 are not subject to adverse effects and as operation of the temperature responsive valve 44 only releases vapor to flow through the heat exchanger which is isolated from the compartment 13,

there is no danger of bodily injury due to direct injection or spray of liquid nitrogen in compartment 13.

The present invention is especially well adapted for use in seagoing vessels because the ship industry is presently using many standard size containers outwardly similar to the container 10 shown in FIG. 1 for handling cargo. A size commonly used is approximately 8 ft. by 8 ft. by 20 ft. The use of standard size containers in conjunction with presently available loading equipment adapted to handle them fully loaded is advantageous because it reduces the handling of the cargo in loading and unloading ships, which results in reduced shipping costs. It is also possible to transfer a container such as the container 10 of FIG. 1 from a ship to a fiat bed truck trailer, or rail car, and deliver the cargo inland by such motor truck, or rail car, without additional handling of the cargo, Special ships are presently in use, called container ships, which are specially designed to efficiently handle cargo in containers outwardly similar to the container 10 shown in FIG. 1. When the container ships are at sea, containers of the capacity of the container 10 may be stowed either on deck or in the hold of the ship.

The liquid nitrogen refrigeration system of the present invention is therefore well suited for containerized cargo handling by seagoing vessels. Moreover, the temperature control is operated by vapor pressure developed within the system and thus no other energy source of any kind is required to operate the system. This is an advantage for combination ship and motor truck container handling because ships and trucks are not presently equipped with uniform standard electrical power supplies suitable for operating control devices.

The present invention is thus adapted for use in cargo vessels using self-contained units such as container 10 of FIG. 1, or several refrigerated containers may be supplied from a single liquid nitrogen source. This last mentioned arrangement is shown in FIG. 6 illustrating a system which can be referred to as a feeder system. A large suitably insulated liquid storage vessel is permanently stored in a container ship 99 in the hold 98, as shown, or other suitable location as on deck. A suitably insulated feeder line 101 connected to vessel 100 is also a part of the permanent installation of the ship. It will be recognized that the vessel 100 can be supplied with liquid nitrogen from a liquid pumper or transport when the ship containing liquid storage container 100 is in port via a suitable fitting 97 in the side of the ship 09. The hold 98 of container ship 99 may advantageously be arranged so that the containers are lowered by deck cranes into fixed slots (not shown). This, of course, fixes the location of each of a plurality of containers 103, 103a, and 103b, and will permit hooking up individual containers 103 and 103a to the feeder line 101 with short flexible lines 104. Each container 103, 1030, has its own refrigeration system generally similar to that of the container 10 of FIG. 1 so that the container operates independently. However, each container is dependent on the vessel 100 for its liquid nitrogen. Several refrigerated containers 103 can thus be placed in the same ship hold and since they operate independently, some containers, for example, container 103a can be set at 0 F., for frozen foods such as shrimp, while other containers such as 1031) may be arranged to maintain higher temperatures, for example, 35 F. for perishable cargo such as lettuce. As it is desired that a somewhat higher temperature be maintained in the refrigerated compartment of container 103k than in the containers 103a, container 1031: may be connected downstream from container 103a so that the relatively cold vapors exhausted from container 103a may be further circulated through the cooling spaces in the walls, ceiling, and floor of container 103k to cool the refrigerated compartment therein, instead of being exhausted directly to atmosphere. Although only a few refrigerated containers 103, etc., are shown in FIG. 6 for clarity,

it will be appreciated that this showing is exemplary only and many more can be carried on one ship.

It will be recognized that refrigerating the containers 103, 103a, and 1031) will generate a substantial amount of spent nitrogen vapor. Therefore, in some instances it may be found advantageous to provide a reliquefier 110 (FIG. of a known type, the details of which have been omitted for brevity, which may be connected downstream of the various containers 103, 103a, and 103b to collect their refrigeration exhausted nitrogen vapors and to reliquefy them by known means. When a valve 105 in the exhaust line for the container is closed and a valve 107 in a line supplying vapor to reliquefier 110 is open, the exhaust vapors from containers 103, 103a, and 1031) will flow to reliquefier 110 for reliquefaction. The vessel 100 and the line 101 may also be suitably connected to reliquefier 110 as indicated in FIG. 6 so that vapor evolved in them may be reliquefied. The reliquefied nitrogen is returned via a liquid line provided with a valve 108 to container 100 for reuse in the system.

However, if desired, the exhaust vapors may be released to atmosphere via a line 106 by closing valve 107 and opening a valve 105 in line 106.

In the event it is necessary for the shipper to deliver a full container of cargo to a destination a considerable distance away from the unloading port one or more of the containers 103a for such destination may be provided with a small auxiliary vessel 109 for holding liquid nitrogen. At the unloading port, and just prior to disconnecting the container 103a from the feeder vessel 100, the internal auxiliary tank 109 is filled with liquid nitrogen. The liquid nitrogen supply for the refrigeration system of container 103a by operating suitable controls and valves may then be switched from the feeder container 100 to operation from the auxiliary tank 109. The container 103a can then be unloaded, placed on a flat bed truck trailer, and delivered to an inland destination with no interruption of the refrigeration system.

The heat exchanger cold vapor passages of the present invention may be located in the container walls so as to substantially uniformly enclose the refrigerated compartment as illustrated in FIG. 1, or when advantageous, the cold vapor passages may be concentrated in the container walls in certain areas for selective cooling and dehydration. For example, the cold vapor passages may be concentrated in one or more side walls, the ceiling, or the floor, or combinations of them, to provide selected areas for cooling and dehydration. Further, the heat exchanger vaporizer and the connected cold vapor passages may be placed either in the long side walls of the container, or in the short end walls, or in the center of these walls, or separately in any combination of them. The heat exchanger vaporizer or cold vapor passages may also be located at the side and end corners of the container where heat flux is generated inwardfrom both the side and end exterior surfaces, or at the top or bottom corners where heat flux is generated inward from three adjacent surfaces, namely, the top or bottom panel, and the associated side and end wall panels, creating maximum heat flux density at these corners. The vapor passages in the selected areas can be connected to the vaporizer in a desired sequence, and either in series or parallel, to place the coldest area in the path of the greatest heat influx, thereby providing the most eflicient heat transfer.

Referring now to FIG. 7 there is shown therein a modification of the present invention in the form of a motor truck of the variety adapted for local delivery of meat or ice cream or other refrigerated food products in which the cold vapor passages are concentrated in selected areas. The truck is provided with a refrigerated container 120 (FIG. 7) mounted on it, having a door (not shown) at the rear end of the container 120 which, of course, must be opened each time the truck operator makes a delivery stop. Opening of the door will allow warm air to enter a refrigerated compartment 129 formed within container 120. Considerable heat thus enters the compartment 129 due to the frequent door openings. The warm. air entering through the door tends to flow upward and along the ceiling 122 of the compartment 129. In order that the cold vapor evolving from a vaporizer 119 in container 120 is not heated too quickly by this warm air near the ceiling, the heat exchanger cold vapor lines near the ceiling are limited to headers at the top of each side wall, and a cross-conduit 124 connecting them to a line 123 leading from the vaporizer 119. The vaporizer 119, which is generally similar to the vaporizer 25 of FIG. 1, is in eificient heat transfer relationship with compartment 129. The headers 125 are connected to vertical channels 126, similar to the channels 31, in the side walls of the compartment for cooling the compartment. by cooling the exterior of its side walls. The system of FIG. 7 includes means for initiating a flow of cold vapor through spaces 126 comprising a controller similar to controller 40, controlling a valve 131, in response to temperature conditions sensed by sensor 132. It should be noted that in FIG. 7 temperature controlled valve 131 is disposed between a suitably insulated liquid nitrogen vessel 121 and the heat exchanger comprising vaporizer 119 and the cold vapor channels 126, in contrast to the arrangement of FIG. 1 in which the temperature controlled valve 44 is disposed between the vaporizer 25 and vapor channel network 31 components of the heat exchanger. The arrangement of FIG. 7 is advantageous in that it responds quickly to restore the desired temperature when an undesirably high temperature condition is sensed in compartment 129, and is therefore desirable in local delivery services involving an input of warm air on each of the frequent openings of the compartment door as described above. Thus cold vapor evolved from the liquid nitrogen in a vessel 121 on sensing of an undesirable high temperature condition in the compartment 129 is delivered substantially directly to the two gas distribution headers 125 in the top portions of the side walls of the container 120. The cold vapor then passes down between the side walls of compartment 129 and container 120 via channels 126. As the cold vapor generated in vaporizer 119 is thus delivered almost directly to the side wall channels 126, there is little or no opportunity for the vapor to be heated by the warm atmosphere just below ceiling 122. The cooling vapor thus reaches the passages formed in the wall of the compartment in the desired relatively cold condition because of the described minimum contact of the vapor passages with the ceiling of the compartment. The vapor from the channels 126 then flows to bottom collection channels 127 and out vertical exhaust conduits 128 at the ends of the sides of the truck body, to atmosphere.

It will be recognized that the vertical exhaust conduits 128, forming outlets for the network of cold vapor passages like the vertically extending channels 31 in the embodiment shown in FIG. 1, utilize the well known chimney effect for venting exhaust gases and therefore the spent vapor rises to the outlet openings at the top of the vertical channels and exhausts to atmosphere at slightly above atmospheric pressure, and thus with a specific velocity.

It will be noted that the liquid nitrogen vessel 121 is shown in FIG. 7 as being separate from the refrigerated container 120 in contrast to the arrangement in FIG. 1 in which liquid gas supply container 20 is enclosed within the refrigerated container 10. The arrangement of FIG. 7 advantageously provides a relatively large refrigerated space within compartment 129, and permits separate mounting of vessel 121 facilitating efiicient utilization of the limited space available on a motor truck. However, if desired, vessel 121 could be enclosed within container 120.

While there has been described what is at present considered to be the preferred embodiments of the invention, it will be understood that various other modifications may be suggested to those skilled in the art and all such are intended to be included within the scope of this invention as best defined in the appended claims wherein there is claimed:

1. Refrigeration apparatus, comprising: a container having internal structure forming a compartment, said internal structure having a ceiling, a floor, and walls joining said ceiling and floor, said ceiling, floor and at least two opposite walls being composed of material capable of efficient heat transfer, external structure spaced about said internal structure, insulation disposed between said internal and external structures, spaced apart channel-like passages formed in said insulation adjacent each of said ceiling, said floor and said two walls and interconnected to establish paths for the flow of vapor through said passages, an elongated vaporizer connected to a source of cold liquefied gas in heat exchange relationship with said compartment, said vaporizer having spaced apart openings communicating directly with said spaced apart passages adjacent said ceiling, and means for venting spent vapor which has reached the ends of said passages adjacent said floor.

2. Refrigeration apparatus, comprising: a container having internal structure forming a compartment, said internal structure having a ceiling, a floor, and walls joining said ceiling and floor, said ceiling, floor and at least two opposite walls being composed of material capable of efficient heat transfer, external structure spaced about said internal structure, insulation disposed between said internal and external structures, spaced apart channel-like passages formed in said insulation adjacent each of said ceiling, said fioor and said two walls and interconnected to establish paths for the flow of vapor through said passages, said ceiling and floor passages extending transversely of said container, a longitudinally extending vaporizer connected to a source of cold liquefied gas in direct heat exchange relationship with said ceiling and extending substantially the length of said ceiling, said vaporizer having spaced apart openings communicating directly with said spaced apart passages adjacent said ceiling, and means for venting the spent vapor which has reached the ends of said passages adjacent said floor.

3. Refrigeration apparatus, comprising: a container having internal structure forming a compartment, external structure spaced about said internal structure, insulation disposed between said internal and external structures, a network of spaced apart passages formed in part by said insulation and in part by said internal structure, at least that portion of said internal structure which forms in part said network of passages being composed of material capable of efiicient heat transfer, an elongated vaporizer connected to a source of cold liquefied gas and having spaced apart openings communicating directly with said network of passages, and remote from the place where said vaporizer opens into said network of passages for venting spent vapor.

4. Refrigeration apparatus, comprising: a container having internal structure forming a compartment, a network of spaced apart passages adjacent said internal structure, insulation surrounding said internal structure and ts related passages, external structure surrounding said insulation, a vaporizer for vaporizing cold liquefied gas, said vaporizer including a first conduit and a second conduit spaced about said first conduit and being in heat exchange relationship with said compartment, said first conduit extending a substantial portion of the length of said second conduit and having an opening communicating with the inside of said second conduit, said second conduit opening at spaced apart locations into said network of passages, and means disposed remotely from the place where said vaporizer opens into said network of passages for venting said network of passages.

5. Refrigeration apparatus, comprising: a container having internal structure forming a compartment, said internal structure having generally parallel passages arranged into a network of passages, an elongated vaporizer in heat exchange relationship with said compartment for vaporizing cold liquefied gas and for distributing resultant cold vapor at spaced apart locations directly to said network of passages, said elongated vaporizer extending substantially the entire length of said container, insulation surrounding said internal structure and its related network of passages, and means disposed remotely from where the vapor enters said network of passages for venting vapor out of said network of passages.

6. Refrigeration apparatus as claimed in claim 5, in which said network of passages includes floor passages formed in said insulation, said remotely disposed means being located at the ends of said floor passages.

7. Method of refrigerating a walled container, comprising the steps of: forming a network of spaced apart flow paths in heat exchange relationship with a substantial part of the container walls, isolating the How paths from the space within the container, vaporizing cold liquefied gas by heat exchange with the container walls, passing the resultant cold vapor at spaced apart locations directly into and through the network of spaced apart flow paths, and venting vapor, after it has been warmed by heat from within the container, out of the network of flow paths to the atmosphere.

8. Method of refrigerating a walled container, comprising the steps of: forming a network of spaced apart flow paths, vaporizing cold liquefied gas by heat exchange with the container, passing the resultant cold vapor at spaced apart locations directly into and through the network of spaced apart flow paths effecting direct heat exchange of the cold vapor with a substantial part of structure forming the container and venting the vapor after it has been warmed by heat from within the container, out of the network of flow paths.

References Cited by the Examiner UNITED STATES PATENTS 2,046,451 7/1936 Grayson 62385 X 2,479,867 8/1949 Rosebaugh 62514 X 2,576,665 11/ 1951 Bixler 62405 X 2,612,028 9/1952 Schnabel 62273 2,850,882 9/1958 Starnes 6252 2,920,462 1/1960 Roser et al 6237 X 2,959,025 11/ 1960 Morrison 62405 X 2,992,546 7/ 1961 Simmonds 62523 3,096,626 7/1963 Morrison 62-64 X 3,127,755 4/1964 Hemery 62267 FOREIGN PATENTS 1,201,722 7/ 1959 France.

ROBERT A. OLEARY, Primary Examiner.

LLOYD L. KING, Examiner. 

5. REFRIGERATION APPARATUS, COMPRISING: A CONTAINER HAVING INTERNAL STRUCTURE FORMING A COMPARTMENT , SAID INTERNAL STRUCTURE HAVING GENERALLY PARALLEL PASSAGES ARRANGED INTO A NETWORK OF PASSAGES, AN ELONGATED VAPORIZER IN HEAT EXCHANGE RELATIONSHIP WITH SAID COMPARTGMENT FOR VAPORIZING COLD LIQUEFIED GAS AND FOR DISTRIBUTING RESULTANT COLD VAPOR AT SPACED APART LOCATIONS DIRECTLY TO SAID NETWORK OF PASSAGES, SAID ELONGATED VAPORIZER EXTENDING SUBSTANTIALY THE ENTIRE LENGTH OF SAID CONTAINER, IN SULATION SURROUNDING SAID INTERNAL STRUCTURE AND ITS RELATED NETWORK OF PASSAGES, AND MEANS DISPOSED REMOTELY FROM WHERE THE VAPOR ENTERS SAID NETWORK OF PASSAGES FOR VENTING VAPOR OUT OF SAID NETWORK OF PASSAGES. 